Rod guides for centralizing sucker rods within production tubing are well known in the art. As shown in FIG. 1, a pumping unit 8 has attached thereto a polish rod 9. The polish rod 9 is attached longitudinally to a sucker rod 10 disposed inside of a tubing (T) which is disposed in a casing string (C). At the bottom end of the sucker rod 10 is a reciprocating pump (not shown). As the pumping unit moves the sucker rod 10 down, the barrel of the reciprocating pump fills with the production fluid to be produced. Conversely, as the pumping unit moves the sucker rod up, a valve in the reciprocating pump shuts and the production fluid in the pump barrel is lifted, displacing production fluid above it and forcing one pump-barrel's worth of production fluid out of the hole.
The sucker rod must extend from the pumping unit all the way down to the reciprocating pump, which may be several thousand feet below the surface. Consequently, the sucker rod is subjected to a variety of stresses: compression, tension, torsion, and bending. The rod is prevented from moving sideways or wobbling by the installation of periodic rod guides 12, 14 on the rod 10 thereby controlling rod and tubing wear. The rod guides typically have a number of vanes, fins or blades which extend radially and centralize the rod within the cylindrical tubing. This prevents the rod from wearing or from other damage. Any wear will, thus, occur to the rod guide fins.
The rod guides may be fabricated from various materials, such as synthetic materials which are oil-resistant and resistant to abrasion.
It is desirable to maximize the material available for wear to maximize the life of the rod guides. Thus, the cross-sectional area of the fins/blades/vanes may be maximized for maximum wear life.
Many prior art sucker rod guides (see U.S. Pat. Nos. 5,115,863; 5,358,041; and 6,152,223) include a body that is molded in intimate contact with the sucker rod. The body has simultaneously molded therewith a plurality of “fins”, “blades” or “vanes” that extend radially from the body. Cross-sections of some prior art rod guides 12 and 14 are illustrated in FIGS. 1A and 1B.